Conventionally, a subscriber of telecommunications services is assigned a telecommunications-network address (e.g., a telephone number) that has no logical meaning outside of serving as the address in the telecommunications system. This means that, in order to reach the subscriber, a caller must translate a logical identifier of the subscriber (e.g., the subscriber's name) into the corresponding network address--a task typically performed by the use of a directory (e.g., a "phone book").
Attempts have been made to achieve a modicum of equivalence between some network addresses and their owners' logical identifiers. For example, the symbol string 5554ATT serves as the North American telephony network address for an AT&T operator, and the symbol string 10MCI serves as the interexchange carrier address for MCI. However, achieving of a great degree of equivalence between network addresses and their owner's logical identifiers is made impossible in most cases by fixed constraints imposed by the network numbering plan of the telecommunications network. Specifically, conventional network numbering plans allow only predetermined fixed lengths and formats for network-number (i.e., network-address) segments, and allow those segments to appear only in predetermined fixed sequences within the number. All network numbers must conform to these constraints. For example, the North American telephone system network-numbering plan requires an extension-number segment to have four digits and to follow an exchange-code segment. The exchange-code segment is required to have three digits, the first one of which cannot be a 0 or a 1, and to follow an area-code segment. The area-code segment is in turn required to have three digits, the first one of which cannot be, and the second one of which must be, a 0 or a 1, and so on. These constraints greatly limit the amount and variety of numbers that the available for assignment as network addresses, and therefore greatly limit the possibility of assigning to subscribers of numbers that do have a logical meaning.
One attempt to overcome this limitation from the caller' s viewpoint is the use of on-line translation directories. These are tables whose contents correlate subscribers' logical identifiers with their assigned network addresses. The tables may be stored and used at individual callers' intelligent telephone terminals, or may be stored in databases that are accessible to local switching systems. Callers place calls by dialing the called subscribers' logical identifiers, which are then translated by the terminals or switching systems by means of the on-line translation directories into the corresponding network addresses, and those corresponding addresses are then used to effect treatment of (e.g., to route) the calls. But these arrangements do nothing to solve the basic problem of dichotomy between a subscriber's logical identifier and network address. Furthermore, they have many of the same constraints as the network numbering plans themselves. For example, known arrangements that allow called-party dialing by name predefine a fixed number of characters for each one of the given-name and sum me segments of the dialed symbol sequence. Consequently, they either require short names to be filled in with null characters to the full specified lengths, and long names to be truncated at the specified lengths, or require end-of-dialing characters to be used to delimit the individual name segments. They also require the given name and surname segments to appear in a predefined sequence. Consequently, they either require the given name to precede the surname, or vice versa, but are not known to allow both options.